Motor fuel containing synergistic anti-knock additive



United States Patent O 3,009,793 MOTOR FUEL CONTAINING SYNERGISTIC ANTI-KNOCK ADDITIVE George W. Eclrert, Wappingers Falls, and Howard V.

Hess, Glenham, N.Y., asslgnors to Texaco Inc., a corporation of Delaware- No Drawing. Filed Mar. 10, 1958, Ser. No. 720,014

6 Claims. (Cl. 44-69) This invention relates to a hydrocarbon fuel composition of high octane rating. More specifically, it involves the discovery that the octane rating of leaded gasoline fuels is substantially improved by the addition of a synergistic additive mixture of a tertiary alkyl ester of monocarboxylic acids and an arylamine.

The recent increases in compression ratios of automobile engines have placed a severe strain on petroleum refiners to produce fuels having the octane rating demanded by these engines. Premium fuels at the present time have research octane ratings between 97 and 100 and it has been predicted that premium fuels will require octane ratings between 105 and 1l0'five years from now in order to satisfy the octane requirements of the high compression automotive engines predicted for that date. In order to produce premium fuels of octane ratings of 97 and above, it has been necessary for refiners to rely heavily on catalytic refining operations such as fluid catalytic cracking, catalytic reforming, alkylation and catalytic isomeri- I zation.

Catalytic cracking and catalytic reforming, which are the most widely used refining operations in the production of high octane fuels, produce .substantial quantities of aromatics; catalytic cracking also produces a substantial amount of olefins. It is well known that olefins'and aro matics, although possessing high octane ratings have a poorer response to organo-lead compounds such as tetraethyl lead than saturated aliphatic gasoline components. Accordingly, as the aromatic and olefinic content of the gasolines have increased to meet the octane levels required by modern automotive high compression engines, the lead response of the resulting fuels has diminished. Stated another way, the octane increment obtainable by the addition of an organo-lead compound decreases as the aromatic and olefin contents of the base fuel increase. The subject invention involves the discovery that the octane rating of leaded motor fuels containing a substantial concentration of high octane components, that is, aromatics, olefins and mixtures thereof, is markedly improved by the addition of a small amount of a mixture of a tertiary alkyl ester of a monocarboxylic acid and an arylamine.

In a commonly assigned copending application, Serial No. 699,944, filed December 2, 1957, it is disclosed that tertiary alkyl esters of monoca'rboxylic acids substantially raise the octane rating of a motor fuel containing an organo-lead anti-knock agent and a substantial concentration' of high octane components which may be aromatic hydrocarbons, olefinic hydrocarbons or mixtures thereof. Arylamines are well known gasoline anti-knock agents. The subject invention involves the discovery that a mixture of t-alkyl esters of monocarboxylic acids and arylamines have a synergistic anti-knock action in motor fuel compositions of this type.

The high octane hydrocarbon motor fuel of this invention comprises high octane components including a substantial concentration of aromatic hydrocarbons, olefinic hydrocarbons or mixtures thereof, an organo-lead-antiknock agent, a tertiary alkyl ester of a monocarboxylic acid, and an arylamine, both of said latter reagents being present in a concentration of at least 0.1 volume percent of the fuel.

in raising the octane rating of gasoline is characterized 3,009,793 Patented Nov. 21, 1961 "ice 2 I The afore-identified copending application discloses that the action of tertiary alkyl esters ofmonocarboxylic acids by several unusual features. First, tertiary alkyl esters appear to be ineffective in raising the octane rating of gasolines unless an organo-lead anti-knock agent, normally tetraethyl lead, is a component of the gasoline mixture. Second, equal concentrations of esters appear to cause a greater octane improvement above the 100 octane level than below the -100 octane level. Third, tertiary alkyl esters appear to have substantially no effect on the octane rating of a gasoline consisting essentially of saturated aliphatic hydrocarbons even though an organo-lead anti-knock agent is present. The synergistic anti-knock additive of the invention comprising a tertiary alkyl ester of monocarboxylic acid and arylamine has the same characteristics and accordingly is effective in a base fuel containing an organo-lead anti-knock agent and a substantial concentration of aromatics and/ or olefins.

The novel fuel compositions of this invention have a minimum concentration of aromatic and/or olefin com- 1 ponents of at least 10 volume percent. The aromatic and/or olefin components of the motor fuel of the invention can constitute as high as 100 volume percent thereof but usually fall between 20 and volume percent. A minimum 10 percent concentration is necessary for the synergistic action of a tertiary alkyl ester of monocarboxylic acid and arylamine in improving the octane rating.

The aromatic components of the motor fuel of the invention are generally supplied by catalytic. reforming or catalytic cracking operations. Catalytic reformate is particularly high in aromatics. The olefin components of the motor fuel of the invention are derived either from thermal cracking, catalytic cracking or polymerization.

The organo-lead reagent necessary for the action of a mixture of a tertiary alkyl ester of a monocarboxylic acid and arylamines as a synergistic octane irnprover is a tetraalkyl lead compound of the class known to possess antiknock action. Tetraethyl lead is practically universally used as an anti-knock agent but other tetraalkyl lead compounds such as tetramethyl lead, tetrabutyl lead, tetraamyl lead, tetrapropyl lead, etc. are known to possess antiknock properties and may be used in the fuel compositions of the invention in conjunction with a mixture of tertiary alkyl esters of monocarboxylic acids and arylamines.

The tetraethyl lead mixtures commercially available for automotive use contain an ethylene chloride-ethylene bromide mixture as a scavenger for removing lead from the combustion chamber in the form of volatile lead halides. As is used hereafter in the examples illustrating the invention, tetraethyl lead fluid denotes the commercial product which comprises tetraethyl lead, ethylene chloride and ethylene bromide, the latter two reagents being present in 1.0 theory and 0.5 theory respectively, theory denoting the stoichiometric amount required for reaction with the lead content of the tetraethyl lead.

The organo-lead reagent is present in the fuel compositions of the invention in concentrations between 0.5 ml. per gallon up to the statutory limit of organo'lead reagent concentration which, at the present time, is 3 ml. per gallon in the case of automotive fuel and 4.6 ml. per gallon in the case of aviation fuel. The usual concentration of tetraethyl lead is between 1 and 3 ml. per gallon in automotive gasoline and 2-4.6 ml. per gallon in aviation gasoline. v

The tertiary alkyl monocarboxylic acid ester compo nent of the synergistic additive of this invention has the general formula: RCOOR wherein R is hydrogen or a hydrocarbyl radical containing l-29 carbon atoms and R is a tertiary alkyl group containing 4-18 carbon atoms. The tertiary alkyl esters of aliphatic monocarboxylic acids,

of .cyeloaliphatic monocarboxylic acids and of aromatic monocarboxylic acids form synergistic anti-knock agents with arylamines in leaded fuels containing a substantial aromatic and/or olefin content. Tertiary alkyl esters effective in the fuel compositions of the invention are the following: t-butyl acetate, t-butyl formate, t-amyl propionate, t-amyl caproate, t-amyl heptanoate, t-octyl pelargonate, t-octyl oaprate, t-butyl 'laurate, t-butyl myristate, .t-amyl palmitate, t-nonyl stearate, t-amyl behenate, t-dodecyl butyrate, tamyl hexanoate, t-dodecyl .o-cumate, t-dodecyl benzoate, t-amyl cyclohexane earboxylate, t-octyl cinnamate, t-amyl phenyl acetate, oleate, t-butyl ester of Snodotte acids (hydrogenated fish oil acids comprising-mainly C to C acids) and t-butyl esters of coconut fatty acids (comprising mainly a mix- ,ture of C to fatty acids).

The preferred tertiary alkyl esters used in the fuel compositions of the invention are derived from aliphatic and aromatic monocarboxylic acids containing 1-14 carbon atoms and from a tertiary alkyl radical containing 4-12 carbon atoms. Preferred tertiary alkyl esters are t-butyl Z-ethylhexanoate, t-butyl benzoate, propionate, t-octyl benzoate, t-butyl hexanoate.

The tertiary alkyl esters must be present in the leaded aromatic and/or olefin-containing compositions of the invention in a minimum concentration of 0.1 volume pert-amyl acetate, t-amyl laurate, t-dodecyl -cent before a synergistic octane appreciation is' realized.

With ester concentrations below 0.1 volume percent, no octane improvement is obtained in leaded gasoline containing at least 10 volume percent aromatics and/or olefins. The preferred concentration of esterin the synergistic additive falls between 0.2 and 1.5 volume percent with maximum results generally being obtained at a concentration level of about 0.5 volume percent. Concentrations of tertiary alkyl ester as high as 5 volume percent can be incorporated in the fuel compositions but no additional synergistic action is realized at the higher concentrations and economic considerations preclude the use of such concentrations in commercial fuel compositions.

The arylamine component of the synergistic anti-knock additive of this invention has the general formula: .RNHR' wherein R is a monocyclic or bicyclic aryl or alkaryl hydrocarbyl radical containing 6 to 16 carbon atoms and R is hydrogen or a hydrocarbyl radical containing 1-12 carbon atoms. The R radical is normally a monocyclic aryl or R radical is usually hydrogen, an aliphatic hydrocarbyl radical containing 1-4 carbon atoms or a monocyclic aryl or alkaryl radical in which the alkyl group contains 1-4 carbon atoms. Only primary and secondary aryl amines react synergistically with tertiary alkyl esters of monocarboxylic acids to improve the octane rating of t-butyl Y alkaryl hydrocarbyl radical. The

leaded gasoline containing the prescribed aromatic and/ or olefin content.

Examples of arylamines which form synergistic antiknock additives with tertiary alkyl esters of monocarboxylic acids are the following: aniline, N-methyl aniline, N-ethyl aniline, N-isopropyl aniline, N-t-butyl aniline, N-n-butyl aniline, o-toluidine, p-toluidine, m-toluidine, N-methyl o-toluidine, N-ethyl o-toluidine, N-t-butyl ptoluidine, diphenylamine, alpha-naphthylamine, di(omethyl phenyl)amine.

Ilse arylamines are employed in a concentration of 0.1 volume percent before a significant synergistic octane improvement is realized with the prescribed concentration of tertiary alkyl esters of monocarboxylic acid. The preferred concentration of arylamine employed in the synergistic anti-knock additive of the invcntion falls between 0.2 and 1.0 volume percent. While concentrations of arylamine as high as 5 volume percent can be used in synergistic combination with tertiary alkyl esters, economic considerations preclude the use of such concentrations in commercial fuel compositions. As a amine is set at approximately 2.0 volume percent.

In Table I there is shown the" synergistic anti-knock i action of mixtures of N-methyl aniline with tertiary alkyl esters in octane gasoline. The base fuel contained 3 cc. of tetraethyl lead fluid per gallonand comprises approximately 10 percent n-butanc, 40 percent isobutaneisobutylene alkylate, 10 percent pentcne from fluid cata- I lytically cracked naphtha and 40 percent heavy platformate. The 105 octane base fuel had an aromatic content of approximately 35 percent, an olefin content of approximately 6 percent, an 1.3.1. of .90 F. and an end point of 367 F.

TABLE I The data in Table I demonstrate clearly the synergistic i anti-knock action of mixtures of N-methyl aniline andi tertiary alkyl esters in 105 octane gasoline. A mixture comprising 0.5 volume percent N-methyl aniline and 0.5 3 volume percent t-butyl benzoate effected a 2.5 units im-i provement in octane rating, whereas separately these concentrations of ester and amine caused a 1.5 and 0.7 unit; octane improvement, respectively. At the 1.0 volume. percent concentration for each component, a mixture of t-butyl benzoate and N-methyl aniline effected a 3.7 units improvement, whereas the individual ester and amine gave only 1.6 and 1.2 unit improvements, respectively. Sim ilar results were obtained with mixtures of N-methyl aniline plus t-butyl ethylhexanoate and N-methyl aniline plus t-butyl acetate.

In Table 11 there is shown the synergistic anti-knock action of mixtures of t-butyl benzoate with aniline and o-toluidine in the 105 octane gasoline employed in Table I.

TABLE II Octane improvement with mixtures of t-butyl benzoate and arylamines Units improvement, research octam number Ester concentration No amine o-Toluldin Aniline 1% (\T.)

No ester t-Butyl benroate, 1.0% (v.) 1. 7

The data in Table H further demonstrate the synergis tic anti-knock action of mixtures of arylamines and ter tiary alkyl esters. A mixture comprising 1.0 volume per cent t-butyl benzoate and 1.0 volume percent aniline e1 fected a 3.7 units improvement'in octane rating wheres the individual component in 1.0-volume percent concer tration gave a 1.7 unit improvement in the ester and 1.1 unit improvement for the aniline. Similarly, a mixtur of 1.0 volume percent t-butyl benzoate and 1.0 volum percent o-toluidine gave 3.0 units improvement wheres the individual components at the 1.0 volume percent CO1 centration gave only a -1.7 unit improvement for the eat and 0.8 unit improvement for the amine.

Obviously, many modifications and variations of th invention as hereinbefore set forth may be made without departing from the spirit and scope thereof and, therefore, only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A hydrocarbon fuel in the gasoline boiling range containing an alkyl lead anti-knock agent in a concentration of at least 0.5 cc. per gallon, high octane components selected from the group consisting of olefinic hydrocarbons, aromatic hydrocarbons and mixtures thereof in a concentration of at least 10 volume percent of said fuel and a synergistic additive combination of a tertiary alkyl ester of the general formula: RCOOR' wherein R is selected from the group consisting of hydrogen and hydrocarbyl radicals containing 1-14 carbon atoms and R is a tertiary alkyl group containing 4-12 carbon atoms and an arylamine of the general formula:

RNHR' in which R is selected from the group consisting of monocyclic and bicyclic aryl and alkaryl hydrocarbyl radicals containing 6-16 carbon atoms and R' is selected from the group consisting of hydrogen and hydrocarbyl radicals containing 1-12 carbon atoms, said ester and amine components being present in concentrations of approximately 1.0 volume percent of said fuel whereby a substantial improvement of the octane rating of said fuel is effected.

2. A hydrocarbon fuel according to claim 1 in which said additive combination comprises N-methyl aniline and tertiary butyl benzoate.

3. A hydrocarbon fuel according to claim 1 in which said additive combination comprises N-methyl aniline and t-butyl Z-ethylhexanoate.

4. A hydrocarbon fuel according to claim 1 in which said additive combination comprises N-methyl aniline and t-butyl acetate.

5. A hydrocarbon fuel according to claim 1 in which said additive combination comprises aniline and t-butyl benzoate.

6. A hydrocarbon fuel according to claim 1 in which said additive combination comprises o-toluidine and t-butyl benzoate.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Improved Motor Fuels Through Selective Blending," Wagner et al., Paper Presented Before American Petroleum Institute, November 7, 1941, pages 8-13. 

1. A HYDROCARBON FUEL IN THE GASOLINE BOILING RANGE CONTAINING AN ALKYL LEAD ANTI-KNOCK AGENT IN A CONCENTRATION OF AT LEAST 0.5 CC. PER GALLON, HIGH ACTANE COMPONENTS SELECTED FROM THE GROUP CONSISTING OF OLEFINIC HYDROCARBONS, AROMATIC HYDROCARBONS AND MIXTURES THEREOF IN A CONCENTRATION OF AT LEAST 10 VOLUME PERCENT OF SAID FUEL AND A SYNERGISTIC ADDITIVE COMBINATION OF A TERTIARY ALKYL ESTER OF THE GENERAL FORMULA: RCOOR'' WHEREIN R IS SELECTED FROM THE GROUP CONSISTING OF HYDROGEN AND HYDROCARBYL RADICALS CONTAINING 1-14 CARBON ATOMS AND R'' IS A TERTIARY ALKYL GROUP CONSISTING OF HYDROCARBON ATOMS AND AN ARYLAMINE OF THE GENERAL FORMULA: RNHR'' IN WHICH R IS SELECTED FROM THE GROUP CONSISTING OF MONOCYCLIC AND BICYCLIC ARYL AND ALKARYL HYDROCARBYL RADICALS CONTAINING 6-16 CARBON ATOMS AND R'' IS SELECTED FROM THE GROUP CONSISTING OF HYDROGEN AND HYDROCARBYL RADICALS CONTAINING 1-12 CARBON ATOMS, SAID ESTER AND AMINE COMPONENTS BEING PRESENT IN CONCENTRATION OF APPROXIMATELY 1.0 VOLUME PERCENT OF SAID FUEL WHEREBY A SUBSTANTIAL IMPROVEMENT OF THE OCTANE RATING OF SAID FUEL IS EFFECTED. 